Modern computer systems in large companies are frequently configured as OLTP systems. OLTP (on-line transaction processing) designates an approach to transaction-based data processing.
In this context a transaction is understood as a series of logically cohesive (frequently database-related) individual actions combined into an indivisible unit. A characteristic of a transaction is that the individual actions combined in it are conducted either in their entirety or not at all. Furthermore, several transactions can be conducted in parallel without causing interactions among them. Each individual transaction therefore runs in “isolation” from the other transactions.
Building on the transaction paradigm, common properties emerge for OLTP systems. One of these common properties is the fact that OLTP systems are shareable. Within the scope of shareable operation a multiplicity of parallel transactions can be generated by different users. OLTP systems are configured in such a way that the transactions (at least in the perception of users) run in real time. Additionally, the transactions are normally typified, i.e. each OLTP system usually provides a series of pre-defined types of transaction for different uses (and with different effects at database level).
Conventional OLTP systems are normally distributed systems in which several client components (or simply “clients”) communicate with at least one host component (or simply “host”). The term component here designates both hardware implementations and software realisations or combinations of hardware and software.
Communication between host and client normally takes place via a network like the Internet or an intranet. The clients request certain services from a host via the network and wait for a response. The host accepts the requests, processes the requests and sends appropriate responses back to the clients. Further components may be arranged between the host and the clients for formatting requests, authenticating clients, etc.
A host normally comprises several individual sub-components (such as transaction-specific application programs, one or more databases and corresponding interfaces), which run on a common system platform. A system platform is understood to be a combination of a certain type of computer and the associated operating system. The host sub-components together with the system platform form a host environment. In many cases there is access to the host environment from a decentralised environment. A decentralised environment of this kind is formed, for example, from the clients distributed over the network in their various forms. In the case of a large bank the various client forms comprise customer terminals, cash machines, customer care terminals, E-banking solutions, etc.
Owing to the rapid progress in the field of information technology and owing to the fact that many existing OLTP systems have already been in operation for a long time, from today's point of view numerous host environments are based on obsolete system platforms. Therefore thought is currently being given to ways in which the host environments, which over the years have become extremely complex systems, can be reliably migrated to new and technologically up-to-date system platforms.
All kinds of problems occur with migrations of this kind. In particular, frequently not all host sub-components can or should be migrated unchanged to the new system platform. In the case of databases the migration is usually also accompanied by changes in content, as information needs change and in general increase. It is also desirable to be able to perform the migration step by step, so that the host environment remains at least partially operable in the event of unexpected problems. Additionally there is frequently a need not to allow the decentralised environment to notice anything of the migration of the host environment.
The invention is based on the object of providing an efficient approach to the migration of a host environment to a new system platform.